Chapter·BiochemistryAmino acid metabolism and disorders

Disorders of aromatic amino acids (PKU, alkaptonuria)Downloads

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1

You are examining a 3-day-old newborn who was delivered vaginally without any complications. The newborn presents with vomiting, hyperventilation, lethargy, and seizures. Blood work demonstrates hyperammonemia, elevated glutamine levels, and decreased blood urea nitrogen. A CT scan demonstrates cerebral edema. Defects in which of the following enzymes would result in a clinical presentation similar to this infant?

ACarbamoyl phosphate synthetase I

BHomogentisate oxidase

CCystathionine synthase

DBranched-chain ketoacid dehydrogenase

EPhenylalanine hydroxylase

2

A 6-month-old boy is brought to a pediatrician by his parents for his first visit after they adopt him from a European country. His parents are concerned about the boy’s short episodes of shaking of his arms and legs; they believe it might be epilepsy. They also note that the child is less responsive than other children of his age. The family is unable to provide any vaccination, birth, or family history. His pulse is 130/min, respiratory rate is 28/min, and blood pressure is 90/50 mm Hg. The boy has a light skin tone and emits a noticeable musty body odor. Which of the following should be supplemented in this patient’s diet?

AIsoleucine

BLeucine

CTyrosine

DPhenylalanine

EHistidine

3

A 30-year-old African American G1P0 mother gives birth to a male infant at 33 weeks' gestation. The mother had no prenatal care and took no prenatal vitamins. The child’s postnatal period was complicated by neonatal sepsis due to group B Streptococcus. He required a two week stay in the neonatal intensive care unit to receive antibiotics, cardiopulmonary support, and intravenous nutrition. He eventually recovered and was discharged. At a normal follow-up visit to the pediatrician’s office one month later, the mother asks about the child’s skin color and hair color. On examination, the child has white hair and diffusely pale skin. The child’s irises appear translucent. Further questioning of the mother reveals that there is a distant family history of blindness. This child most likely has a defect in an enzyme involved in the metabolism of which of the following molecules?

ALeucine

BHomocysteine

CPhenylalanine

DHomogentisic acid

EDOPA

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